The study found that exposure to delinquent peers had consistent effects on the initial level of antisocial behavior in most analyses of delinquency and substance use, and some effects persisted into later adolescence. Individual self-control had a significant effect on the latent growth factors on a number of tests for the delinquency measures, but no significant effects in the analysis of substance use. Although the analyses identified some effect of family influence and socioeconomic status (SES), these factors were inconsistent across cohorts and outcome measures. The data analysis suggested that trajectories of delinquency and substance abuse varied across neighborhoods. First, although current best practices with at-risk youth are built around family-based programming, situational/peer risk should be central to the development of prevention and intervention during adolescence. Second, the robustness of delinquent peer exposure as a significant influence on delinquency and substance use, even in the cohort observed starting in late childhood, suggests the need to develop interventions that can counteract this risk. Regarding community-based interventions, it is important to identify community-based factors that may counteract negative peer influences. The PHDCN used multi-wave data for three youth cohorts spanning ages 9 to 19.
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